Fluid pressure tool



Aug. 15, 1932' G. M. NELL I I FLUID ,PRESSURE TOOL Filed Oct. 16, 1929 T N @A w u m w m @f m XS. M x m J. ,f Y? w am y B Rt Patented Aug. 16, 1932 UNiTsD STATES GUSTAVE M. NELL, OF DETROIT, MICHIGAN, ASSIGNOR TO CHICAGO PNEUMAEYC TOOL Y v(.`Ol!LlP.ANY,.OF NEW YORKyIN. Y., `A CORPORATION OF NEW JERSEY FLUID PRESSURE TOOL Application filed ctober 16, 1929. SeraINo, 399,888.

This invention relates to fluid pressure tools of the percussive type having automatically thrownV valves for controlling the distribution of motive fluid. In certain respects it may be considered as an improvement upon, or further development of, the

invention disclosed in my copending application Serial No. 314,893, filed October 25, 1928, issuedas Patent No. 1,796,389on March 17,1931. v

Among the objects of the invention are to increase the positiveness ofV actuation of the moving parts in tools of the described type, to cause the hammer piston to have a long or full rear stroke with a minimum amount of motive fluid, to increase the rotational torque in rifle bar rotation machines or tools, and in general to improvev prior tools and to .increase their eiiiciency. In order to illustrate the invention one concrete embodiment thereof is shown in the accompanying drawing in which:

Fig. 1 is a longitudinal sectional view; Fig. 2 is a fragmentary sectional view on C, an enlarged scale of the tool shown in F ig, 1

with the valve and tions;

Fig. 3 `is a left-end elevational view, on the scale of Fig. 1, of the cylinder with4 the baclrheadV and the cylinder ring removed. The embodiment of the invention chosen for the purpose of illustration comprises a pneumatic percussive tool having a cylinder 4 providing a piston chamber Within which reciprocates an impactmember or piston 5 arranged to impart blows to a'worlring tool, such as a drill steel 6, supported in a rotary chuck 7 mountedin front head 8 secured to cylinder 4. Cylinder 4 is provided with an exhaust chamber formedby a transverse annular groove 9 substantially centrally of the piston chamber and communicating directly piston in different posi.-

with atmosphere through one or more ports 10. This exhaust chamber is controlled by piston 5 and is arranged to be overrun by the latterin both directions. v

A rotary impulse isimparted to piston 5 during its reciprocations by conventional mechanism comprising `a riiernut 11 supported in the recessed portion of piston 5 and slidably receiving a rifle bar 12 having ratchet mechanism supported in back head 13, the rifle -bar projecting through and having a bea-ring in cylinder rino' 14 which is held in place by back head 13. ,lliston 5 has a 'fluted or ribbed extension 5a for transmitting the rotary impulse of the same. t

chuck Cylinder 4 also provides a valve chamber in which is disposed an automatically thrown valve 15 arranged to move intimed relation withv piston and to control the distribution of motive fluid from inlet 16 Vto opposite ends of the piston chamber to drive the piston in both directions. Valve is of'substantial length and is disposed in parallelism with the piston chamber and closely adjacent thereto so that the connecting ports and passages are relatively short and direct.

Motive fluid for driving the piston on its Working stroke (Fig. 1) enters the piston Eric Y' chamber by a port 17a from chamber 17 under control of the rear end vof the valve and motive fluid for the return stroke (Fig. 2) passesV axially through the bore'of valve 15, thence transversely into valve chamber 18 axially through passages 19 to chamber 2O and thence through a port 20a directly into vthe piston chamber. The ends of valve 15 are differential 4in size therebyproviding dierential pressure areas, the smaller area 21'being at the left or rea-rend 'ofl the tool andthe larger area 22 being at the forward end.V Ashoulder 21a adjacent the small end of the valve and always in communication with the rear end of the piston provides a compressionarea subjected to air trapped and compressed by the piston to shift the valve to the forward position (Fig. 1). Near the` compression area 21a valve 15 has an external enlargement or ange 23 providing a shift area 24 in chamber 25, which area is opposed to areas 21 and 21a and is greater than the sum of the latter. Both faces of flange 23 are continuously vented to atmosphere, the rearward face by a lby a passagepl tocexhaust chamber 9. The fluid pressure tool, as heretofore described,

' for. the front end .of the piston, this exhaust utilizing main exhaust chamber 9 and being under control of valve 15, the air ahead of the piston passing out through inlet port 29a, chamber 20, axial passage y19,-valve chamber 18, around and along an exterior groove 29' in the valve to valve chamber 3() Yand thence is similar, so far as pistonand valve operation is concernethto that disclosed in my aforesaid copending application, Serial No. 314,893, filed October 25, 1928,'and the cycle of operation is identical. l I

To secure full eiiiciency of the tool and to provide for a` powerful piston blow and strong and positive rotation of the drill steel whenrifle bar mechanism is used-as herein shown, it is important that the piston be caused to make along rearward stroke under any conditions of operation. To those skilled in this art, it is a well knownfactthat in the type of mechanism shown, under heavyrota-- tional'load on the rotation train, there isa tendency for the vpiston to short stroke or flutter with high'mean effective pressure on both sides of the piston and loss in rotative power, unless a special provision is made to avoid same. To this end an additional vent is provided for the rear end of the piston chamber during the back stroke of thepistonto delay the trapping of air inthe rear end of the piston chamber and the'consequent early shifting of the valve through the building up of pressure against compression area 21a on the valve. This auxiliary vent comprises a port 33 opening into the rear piston chamber intermediateV shift passage 28 and inlet port 17d.. V1Vent port 33, which is controlled by Y'piston 5 communicates, as indicated, bypassage 33a with valve chamber 34, which chamber, in the rearward position of the valve (Fig. 2) is placed in communication with exhaust valve chamber SO by annular groove 29 in valve 15 with the result that this auxiliary vent is closed when the valve is in its forward positiony (Fig. 1) for` the power or working stroke of the tool. rThrough the connection of exhaust chamber 30 around the valve by passage 81 with main exhaust chamber 9 of the cylinder, it will be evident that the fluid vented through auxiliary vent port 33 passesv to atmosphere through main cylinder exhaust 9 and atmospheric ports 10.

While the invention has vbeen herein disclosed in what is considered to be its preferred form, it is to be understood that the invention is notlimitedvto the specific details thereof, but covers allchanges, modifica tions, and adaptations within the scope of the appended claims.

I claim as my invention:

l. In auid pressure motor, a cylinder providing a piston chamber, a piston reciprocable therein,a fluid pressure valve, one end of which controls admission of fluid pressure to one end of said piston chamber and the other end of said valve to the other end of said piston chamber', said valve having only one compression area constantly in communication with one end of said piston chamber and a shift area opposed to said compression area, means intermittently bringing said shift area into communication with said piston chamber including a port controlled by said-piston, a continuously open vent for said shift area, and means intermediate 'said port vand said end of said piston chamber providing an additional vent under control of said piston and of said valve and operable only after movement of said valvev by action of pressureiluid on said shift area.

2. In a fluid pressure motor, a cylinder pro-v viding a piston chamber, a piston reciprocable therein, a fluid pressure valve, onev end of which controls admission of fluid pressure to one end of said piston chamber and the other end of said valve to the'other end of said` piston chamber, said valve having only one compression area constantly in communication with one end of said piston chamber and a shift area opposedtosaid compression area, means intermittently bringing said shift area into communication'with said piston Vchamber including aport controlled by said piston, a continuously open vent for said shift area, and venting means for said end of said piston chamber controlled by said valve andinclnding a port intermediate said first named port and said end of said piston chamber for effecting a predetermined delay in the shifting of the valve under compression, said last-named venting means *beingV operable subsequent: to movement of. saidfvalve by I'ness'urek fluid admitted through said first-named port against'fsaid shift areaA i 8. Inza fluid pressuremachine for rotating and imparting blows to a working tool, a cylinder providing a pistonichamben'a piston reciprocable therein, an automatically thrown valve controlling with its ends' the admission of motive fluid to the opposite ends of said piston chamber, means for rotatably supporting the working tool in position to receive the blows of said piston, rotation mechanism for said toolactuated by the reciprocations of said piston, said valve having a compression area constantly in communication with one end of said piston chamber and a shift area opposed toV said compression area, means iintermittently bringing saidv shift area into communication with said piston chamberineluding af port controlled by'said piston, a continuously open vent for said shift area serving as an auxiliary exhaust for the piston chamber on movement of said piston in one direction, and means intermediate said port and said end of saidpiston chamber under control of both said piston and said valve to provide an additional vent for insuring a substantially full stroke of said piston in said direction. Y

4. In a iuid pressure machine for rotating and imparting blows to a working tool, a cylinder providing a piston chamber, a piston reciprocable therein, an automatically thrown valve controlling with` its ends the admission of motive fluid to the opposite ends of said piston chamber, means for rotatably supporting the working tool in position to receive the blows of said piston, rotation mechanism for said tool actuated by the reciprocations of said piston, said Valve having a compression area constantly in communication with one end of said piston chamber and a shift area opposed to said compression area, means intermittently bringing said shift area into communication with said piston chamber including a port controlled by said piston, a continuously open vent for said shift area serving as an auxiliary exhaust for the piston chamber on movement of said piston in one direction, and additional venting means under control of both said piston and said valve for said end of said piston chamber.

Signed by me at Detroit,in the county of Wayne and State of Michigan this 10 day of October, 1929.

GUSTAVE M. NELL. 

